Conventional implements for stirring or comminuting food are known, for example, from WO 96/10944 A1 or EP 0 724 857 A1. A wide variety of such implements are being used particularly in daily food preparation, to comminute and blend foodstuffs, for example. One kind of implements that have become widespread in private households, but also in professionally run gastronomy venues, are hand blenders. Such hand blenders typically have a motor housing which adjoins an elongate housing part, the so-called stem, which in turn merges at its end into a shield having an open-bottomed end, the so-called bell. In the motor housing, a drive motor is arranged which drives a working shaft that is inserted through the stem and usually has attached at its end, in the region of the bell, a working part, for example a cutter in the form of a rapidly rotating blade in order to mix liquids and comminute solid foods.
The stem generally performs the adaption of the motor housing to the stem assembly and frequently supports, in an axial and radial direction, the shaft required for driving the cutter. The bell primarily has a protective function of making it more difficult for the user to contact the blade. Moreover, it serves to define a fixed distance between the blade and the bottom of the processing container (pot, blending beaker, etc.), optimize the flow around the blade and protect against splashes when immersed into liquids. The bell is dimensioned so as to completely enclose the cutter and to protrude a certain distance beyond the end of the shaft or the cutter as viewed in the direction of the axis of the working shaft.
In these devices that are available on the market, the blades are always fixed at a defined horizontal position within the bell. The blades are always fixedly mounted on a shaft and are mostly supported in a radially and axially rigid manner. The resulting processing space that can be reached by the cutter is thus limited. The “normal” upward and downward movement of the entire hand blender by the user makes this space only marginally larger. At the latest when the bell touches the bottom to be worked on, the space below the cutter is no longer reached by the cutter. Comminution then generally takes place only by way of flow effects. The product being cut is drawn along through the processing space by the flow and is thus comminuted, provided there is enough liquid around the product being cut.
Furthermore, in the known hand blenders, the stem may adhere by suction to the bottom of the container over and over again during processing, which may be extremely bothersome to the user since an increased amount of force is required to get the stem off the bottom again. This is mainly due to the position of the cutter within the bell, since the geometry of the cutter, which is helpful for its function, provides for a “propeller effect” and causes the entire stem to be adhered to the bottom to be worked on.
In order to avoid this adherence, the applicant has proposed a hand blender with an elastically deformable bell in DE 197 50 813 C2. When the hand blender is placed on the bottom in the blending beaker during processing, the bell can deform due to axial pressure exerted by the user and can thus bring the cutter closer to the container bottom and consequently displace the cutter axially in relation to the edge of the bell.
Another approach has been proposed by the applicant with the hand blender of DE 195 04 638 A1, in which the negative pressure occurring during adhesion is eliminated by a valve disposed in the bell as a flow channel. In a further embodiment, an rpm-dependent relative displacement of bell and working part is performed in order to open an additional flow channel.
However, the means for displacing the shaft which are required for this are extremely complicated mechanically and thus very expensive. In addition, the user cannot himself determine the position of the blade in relation to the bell as a whole in order to bring the blade closer to large pieces of food which would not otherwise be picked up by it, and also to freely displace the blade axially in the processing space of the bell. The reason is that it frequently happens that a larger piece of the material being cut gets stuck in the region below or above the cutter and cannot be comminuted by the edges of the blade. Moreover, some pieces of food lie flat on the bottom of the pot so that the cutter cannot reach them. This increases the processing time, and the result will be of inferior quality, too.
A hand blender having the features is known from document DE 698 26 868 T2.